Fixing the position of a planet gear pin

ABSTRACT

A planet gear pin ( 4 ) is secured against axial displacement relative to a planet gear carrier ( 1 ) using an elastically deflectable or deformable retaining element ( 9, 9   a,    9   b ) arranged in a location hole ( 10 ) in the planet gear pin ( 4 ).

FIELD OF THE INVENTION

The invention relates to a planetary gear with a planet carrier andplanet gears, which mesh by means of teeth with a ring gear on one sideand with a sun gear on the other side, wherein the planet gears canrotate on planet gear pins by means of roller bearings and the planetgear pins are held in location holes of the planet gear carrier.

BACKGROUND

Such planetary gears are sufficiently well known to someone skilled inthe art. In the interior of a planet gear set, the so-called sun gearturns on a central shaft. Several gears having teeth that engage in theperipheral teeth of this sun gear are provided, in practice usuallythree to five, which are designated as planet gears due to their obviousarrangement. And as planets, as they rotate they also move in a circularmotion about the sun gear, while they simultaneously turn about theirown axis. The shafts of the planet gears are fixed on the planet gearcarrier, which receives this rotational movement, that is, likewise inthe rotational direction about the central axis. As a third element, thering gear surrounds the entire formation, in that it engages the planetgears with its internal teeth from the outside. Here, the central axisalso represents the center of rotation.

The shafts of the planet gears are also designated as planet gear pinsand are fixed in the planet gear carrier in various ways.

According to DE 196 11 605 A1, this is realized in that both the planetgear carrier and also the planet gear pins are provided with radiallyextending holes, in which attachment screws are inserted. After beingscrewed in, the screw bodies of these attachment screws are both in theplanet gear pin and also in the planet gear carrier, so that the planetgear pins are secured against axial displacement. It is obvious thatsuch a position-fixing device of the planet gear pin is verycomplicated. First, both in the planet gear carrier and also in theplanet gear pin, the location holes are to be formed and provided with acorresponding internal thread. Then, both are set relative to each otherin the peripheral direction so that the holes align, before finally, theattachment screws can be inserted.

Another such type of attachment follows from the German Utility ModelApplication DE 74 181 66 U. This is realized in that first a hoop ringis pushed onto the planet gear pin. The ring is connected to the pin bymeans of a weld. Then, the planet gear pin is secured by means of aretainer ring, which engages in an annular groove of the collar ring andsecures this against axial displacement. Here, it can also be recognizedthat such an attachment of the planet gear pin in the planet gearcarrier is very complicated and costly.

Finally, in DE-OS 25 03 518, another type of attachment of the planetgear pin in a planet gear carrier is described. FIG. 2 of this priorpublication shows a planet gear carrier comprising two disc-shapedsheet-metal parts welded to each other with a planet gear. The planetgear pin is held in two aligned holes of the two sheet-metal parts ofthe planet gear carrier. The pin is fixed in that it is stamped at itstwo end sides. Now, in this respect, it is known to someone skilled inthe art that the planet gear pin is subjected to very high loads andtherefore must be subjected to a hardening process before beinginstalled in the planet gear gear. Now, in order to carry out stampingof the pins in general at the two opposing end surfaces, they must besubjected to a soft-annealing process. It is obvious that such a processis also very complicated and thus expensive.

SUMMARY

Therefore, starting with the disadvantages of the prior state of theart, the invention is based on the objective of reducing expense in themanufacturing or assembly process of a planetary gear through a simplertype of attachment of the planet gear pin in the planet gear carrier.

According to the invention, an axial displacement of the planet gear pinin the planet gear carrier is prevented by an elastically deflectable ordeformable retaining element, which, on one hand, engages in a locationhole in the planet gear pin and, on the other hand, covers the planetgear pin and planet gear carrier in the radial direction.

It is obvious that such a type of attachment is considerably simplifiedrelative to the prior state of the art, because only one retainingelement connecting the planet gear carrier and planet gear pin has to bepushed into the location hole of the planet gear pin. After its elasticexpansion or deformation, a secure hold of the two parts to each otheris guaranteed.

Other advantageous configurations of the invention are described below.

The retaining element has a circular ring-type region extending in theradial direction. Bars extend from this region in the axial direction inthe shape of a pipe and are separated from each other in the peripheraldirection by axis parallel slots and have locking cams projectingradially outwards at their free ends.

In an advantageous improvement of the invention, the circular region ofthe retaining element should be provided in its center with a passage.This is required if the roller body of the planet gear is to be suppliedwith lubricant via the retaining element and the planet gear pin.

This retaining element is produced from spring steel or from plastic.

A notch is machined into the location hole of the planet gear pin. Anannular retaining surface for the locking cams of the retaining elementis formed by this notch. In this way, a secure locking connection isformed between the retaining element and the planet gear pin.

Another improvement of the solution according to the invention isseveral retaining elements are connected to each other in the peripheraldirection by a radially extending circular ring, from which they extendin the axial direction, so that a compound retaining element is formed.This is especially advantageous, because, for example, in a planetarygear with five planet gears, five retaining elements do not have to behandled individually, instead only one.

In another improvement of the invention, several retaining elements areconnected to each other in the peripheral direction by a hollow bodythat is open towards one side, so that a compound retaining element isformed.

The hollow body comprises two radially extending circular rings, whichare spaced apart from each other in the axial direction and which areconnected at their outer extent by an axially extending back part,wherein there is a passage that extends to the space between the twocircular rings in the circular ring which is connected to the retainingelements.

The advantage of this arrangement lies not only in a simple connectionof several retaining elements, but it also lies in the fact that thisretaining element combined according to the invention can be usedsimultaneously for improved directed oil guidance in planetary gears.Thus, retention and directed oil guidance functions are combined intoone. According to the prior state of the art, the oil guidance functionwas realized through complicated additional retaining sheets.

The invention is described in more detail using the followingembodiments.

BRIEF DESCRIPTION OF THE DRAWING(S)

Shown are:

FIG. 1 is a partial longitudinal section through a planetary gear.

FIG. 2 is a enlarged perspective view of a retaining element accordingto the invention as a single part.

FIGS. 3 and 4 are a side view of a compound retaining element without anoil guidance function.

FIGS. 5 and 6 are a section and a perspective view, respectively, of acompound retaining element with an oil guidance function,

FIG. 7 is a partial longitudinal section through a planet gear, and

FIG. 8 is a longitudinal section through a planet gear carrier accordingto the prior state of the art.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

The planet gear carrier 1 shown in FIG. 8 according to the state of theart has two side walls 2, 3, in whose location holes planet gear pins 4are fixed. On these pins, planet gears 6 can rotate by means of bearingarrangements 5. The teeth 7 of these gears mesh with a not-shown hollowgear on one side and with a similarly not-shown sun gear on the otherside. FIG. 2 shows how the planet gears of the present invention haveteeth that mesh with a ring gear 14 on one side and a sun gear on theother side. FIG. 8 also shows stopping plates 8, which typicallycomprise a material with good sliding properties, such as, e.g., sheetmetal plated with bronze, which thus reduce the friction between theplanet gears 6 and the planet gear carrier 1, are arranged on the planetgear pin 4 on both sides of the planet gears 6. As FIG. 8 further shows,the planet gear pins 4 are fixed in the location holes of the side walls2, 3 of the planet gear carrier 1 by stamping. That is, the retention ofthe planet gear pin is realized by material displacement on the twoopposing end sides of the planet gear pin 4. However, as alreadyexplained explicitly in the introduction under the state of the art,such an attachment of the planet gear pin 4 in the planet gear carrier 1is very complicated.

In FIG. 2, a retaining element 9 according to the invention is shown,which includes a circular base region 9.1. Bars 9.2, which are separatedfrom each other in the peripheral direction by axis parallel slots 9.3,are arranged in the shape of a pipe, and extend from this base region inthe direction of the longitudinal axis 9.5. It is clear that in thisway, a radially inward or outward deflection of the bars 9.2 ispossible. On their free ends, the bars 9.2 have locking cams 9.4 spacedapart from each other in the peripheral direction.

The planet gear shown in FIG. 2 comprises the planet gear 6, which isarranged on the planet gear pin 4 and whose teeth 7 mesh with teeth 13.1of the sun gear 13. The planet gear 6 is supported by the bearing 5,wherein stopping plates 8 are arranged on both sides between the planetgear 6 and the planet gear carrier 1. As FIG. 2 shows further, theplanet gear pin 4 is held in the location holes 1.1 of the planetcarrier 1. The planet gear pin 4 is equipped on both sides with anaxially extending location hole 10, which has a notch 10.1, so that aretaining surface 10.2 is formed. As can be further seen from FIG. 2,the retaining element 9 covers with its circular region 9.1 in theradial direction both the end side of the planet gear pin 4 and also apart of an end side of the planet gear carrier 1. When the retainingelement 9 is pushed in, its bars 9.2 are guided inwards due to theirelasticity in the radial direction and spring radially outwards afterreaching the notch 10.1, so that the locking cams 9.4 of the retainingelement 9 contact the retaining surface 10.2 of the notch 10.1. Thelocation hole 10 arranged on the right side in the planet gear pin 4 isextended in the direction of the pin middle and provided with radialholes 10.3, which open into the raceway region of the bearing 5. In thepresent embodiment, both the retaining elements 9 arranged on the leftside and also on the right side are provided with a passage 9.6, so thatthe bearing 5 can be provided with lubricant from the outside via thepassage 9.6, the location hole 10, and the radial holes 10.3 branchingaway from the location hole.

If a planetary gear is equipped, for example, with three planet gears 6,then it has proven to be advantageous to connect three individualretaining elements 9 to the circular ring 11, such that these elementsare arranged at three peripheral positions spaced apart from each otheruniformly and so that they extend from this ring in the axial direction.In this way, a compound retaining element 9 a is formed, whichsimplifies the assembly of the planetary gear with the provided threeplanet gears. Such a retaining element 9 a is shown in FIGS. 3 and 4.

In FIGS. 5 and 6, a compound retaining element 9 b with oil guidancefunction is shown. As can be seen from this, three individual retainingelements 9 that are spaced apart from each other uniformly in theperipheral direction are connected to the hollow body 12, which iscombined from two circular rings 12.1, 12.2 that are spaced apart fromeach other in the axial direction and are connected to each other attheir outer side by the back part 12.3, so that the formed hollow body12 is open towards its inner side. As can be seen in the top part ofFIG. 5, in the connecting region of the retaining element 9 and circularring 12.2, this is provided with a passage 12.2.1, so that this compoundretaining element 9 b can perform an oil guidance function, as shown bythe arrows.

Finally, in FIG. 7 a planetary gear is shown, whose planet gear pins 4are secured in the planet gear carrier 1 in the same way, but in adifferent construction. While this is achieved on the left side with thecompound retaining element 9 a, it is realized on the right side withthe compound retaining element 9 b. In the ready described way, theleft-side retaining element 9 a is combined from several individualretaining elements 9, which are connected to each other by the circularring 11. In contrast, the right-side retaining element 9 is equippedwith a directed oil guidance function, which is realized by acombination of individual retaining elements 9 with the hollow body 12open towards the inside. Thus for the retaining element 9 b, theretaining and lubricant guidance functions are combined into one. Thepath of the lubricant through the planetary gear is realized from theoutside towards the inside first via the hollow body 12, then via thepassage 12.2.1 into the axially extending location hole 10. From thishole, it is led via the branching radial holes 10.3 into the racewayregion of the bearing arrangement 5.

REFERENCE SYMBOLS

Planet Gear Carrier

-   1.1 Location hole-   2 Side wall-   3 Side wall-   4 Planet gear pin-   5 Bearing-   6 Planet gear-   7 Teeth-   8 Stopping plate-   9 Retaining element-   9 a Retaining element-   9 b Retaining element-   9.1 Circular region-   9.2 Bar-   9.3 Slot-   9.4 Locking cam-   9.5 Longitudinal axis-   9.6 Passage-   10 Location hole-   10.1 Notch-   10.2 Retaining surface-   10.3 Radial hole-   11 Circular ring-   12 Hollow body-   12.1 Circular ring-   12.2 Circular ring-   12.2.1 Passage-   12.3 Back part-   13 Sun gear-   13.1 Teeth-   14 Ring gear

1. Planetary gear comprising a planet gear carrier and planet gearshaving teeth that mesh with a ring gear on one side and with a sun gearon the other side, wherein the planet gears rotate via roller bearingson planet gear pins and the planet gear pins are held in location holesof the planet gear carrier, wherein axial displacement of the planetgear pins in the planet gear carrier is prevented by an elasticallydeflectable or deformable retaining element, which engages in arespective location hole in the planet gear pin and covers the planetgear pin and planet gear carrier in a radial direction, wherein severalof the retaining elements are connected to each other in a peripheraldirection by a hollow body that is open towards one side, so that acompound retaining element is formed.
 2. Planetary gear according toclaim 1, wherein each of the retaining elements has a radially extendingcircular region, from which, bars extend in an axial direction that arearranged in a pipe shape and are separated from each other in aperipheral direction by axis parallel slots and have locking camsprojecting radially outwards at free ends thereof.
 3. Planetary gearaccording to claim 2, wherein the circular region is provided with apassage in a center thereof.
 4. Planetary gear according to claim 2,wherein a notch, which forms an annular retaining surface for thelocking cams of the retaining element, is provided in the location holeof the planet gear pin.
 5. Planetary gear according to claim 1, whereinthe retaining element is manufactured from spring steel or from plastic.6. Planetary gear according to claim 1, wherein several retainingelements are connected to each other in a peripheral direction by aradially extending circular ring, from which the retaining elementsextend in the axial direction, so that a compound retaining element isformed.
 7. Planetary gear according to claim 1, wherein the hollow bodycomprises two radially extending circular rings, which are spaced apartfrom each other in the axial direction and which are connected to eachother at their outer extent by an axially extending back part, a passageis defined in the back part to the space between both circular rings inthe circular ring connected to the retaining elements.
 8. Planetary gearcomprising: a planet gear carrier and planet gears having teeth thatmesh with a ring gear on one side and with a sun gear on the other side,wherein the planet gears rotate via roller bearings on planet gear pins,and the planet gear pins are held in location holes of the planet gearcarrier elastically deflectable or deformable retaining elements engagein respective location holes in the planet gear pins and cover theplanet gear pin and planet gear carrier in a radial direction to preventaxial displacement of the planet gear pins in the planet gear carrier,each of the retaining elements has a radially extending circular regionfrom which a hollow bar axially extends perpendicular to the circularregion, said hollow bar having at least one slot therein, and at leastone locking cam projects radially outwardly at a free end of said hollowbar.
 9. Planetary gear according to claim 8, wherein the circular regionis provided with a passage in a center thereof.
 10. Planetary gearaccording to claim 8, wherein the retaining element is manufactured fromspring steel or plastic.
 11. Planetary gear according to claim 8,wherein a notch, which forms an annular retaining surface for thelocking cams of the retaining element, is provided in the location holeof the planet gear pin.
 12. Planetary gear according to claim 8, whereinseveral of the retaining elements are connected to each other in aperipheral direction by a radially extending circular ring, from whichthe retaining elements extend in the axial direction, so that a compoundretaining element is formed.
 13. Planetary gear according to claim 8,wherein several retaining elements are connected to each other in aperipheral direction by a hollow body that is open towards one side, sothat a compound retaining element is formed.
 14. Planetary gearaccording to claim 8, wherein the hollow body comprises two radiallyextending circular rings, which are spaced apart from each other in theaxial direction and which are connected to each other at outer portionsthereof by an axially extending back part, and a passage is defined inthe back part to the space between both circular rings in the circularring connected to the retaining elements.